6.4.5 Bovine Ostertagiosis Flashcards
What are the characteristic signs of parasitic gastroenteritis (PGE)?
diarrhoea / weight loss (clinical disease)
poor weight gain (sub-clinical disease)
seasonal appearance
hypoalbuminaemia (low blood protein lvl)
What are the most important worm species that can cause bovine PGE?
Ostertagia - causes ostertagiosis, in abomasum
Cooperia - not as pathogenic as ostertagia bit the most numerically important roundworm in SI of cattle
Nematodirus - can cause clinical signs in first season cattle
What do adult Ostertagia ostertagi worms look like?
Where can they be found?
1cm long, cotton-like, brown (when fresh)
found in the abomasum (fundus)
Outline the life cycle of Ostertagia ostertagi
eggs shed from the host in faeces
egg hatching
1st stage larva -> 2nd stage larva
eggs and larvae free-living on the pasture
3rd stage larva becomes infectious
ingested by the new host
passes to abomasal gastric glands, where develops into 4th stage larva
then develops to an adult
leaves glands and sheds eggs
What is a pre-patent period?
How long is it for Ostertagia ostertagi?
period from ingestion of infectious larvae to first eggs visible in faeces
for Ostertagia it’s 3 weeks to 6+ months
Describe the Ostertagia egg
oval
thin egg wall
transparent
brownish embryonic cells (blastomeres)
Describe the 3rd stage larva
keeps sheath of L2 as an overcoat
that allows it to survive 9-12 months on the pasture
infective stage
What does the rate of infection depend on?
host appetite
numbers of infective larvae (L3) on pasture
Explain the epidemiology of ostertagiosis in dairy herds
disease type 1
Type 1 disease (summer)
over winter L3 survive in pastures
March - new cows on pasture ingest L3
April - June L3 on pasture dying (not enough food) BUT
3 weeks from ingestion new eggs get on pasture
August - larvae reach L3 (temperature dependent)
calves eat that - Auto-infection peak (August - November)
Explain the epidemiology of ostertagiosis in dairy herds
disease type 2
PRE-TYPE 2 STAGE: when calves housed during winter (from December) larves EL4 in arrested stage in abomasal mucosa
March - EL4 resume development and emerge in waves
we see intermittent diarrhoea in the herd
Explain the epidemiology of Ostertagiosis in beef herds
in spring calving
spring mortality of L3 occurs before calves eat much grass
immune cows eat most grass and pass few eggs
disease risk very unlikely
Explain the epidemiology of Ostertagiosis in beef herds
in autumn calving
calves graze before spring mortality of L3
cows eat most grass with L3 (so calves get less)
so risk higher but still low compared to dairy herds
How does the immunity to Ostertagia develop?
slow to develop (whole grazing season)
may fall over winter - re-established upon turnout (2nd grazing season)
adult cattle solidly immune (no significant role in disease epidemiology)
How can we control the type 1 disease?
Use clean pasture
Delay turnout until after spring mortality in L3
Dose’n’move to aftermath (mid-July)
